||Carbon monoxide as a useful C1 source has been received great attention in the chemical industry. In particular, CO shows a high reactivity toward various organic compounds in the presence of transition metal catalysts. Palladium catalysts promoted reactions of CO with ethylene or propylene to form polyketones, new attractive engineering plastics. Although the commercial process of polyketone has been established, there are problems e.g., the reactor fouling which needs to be resolved for the mass production. In this presentation, we will show a systematic design and synthesis of nanosized-palladium catalysts, and their control of the polymer fouling.